1. Field of the Invention
The present invention relates to cell transfer apparatus and methods using a variable rate codec and more particularly to a cell transfer apparatus and method which determines a sequence number of each cell by adding a weight-corresponding to a time required for encoding data.
2. Description of the Related Art For example, a voice waveform which is data to be transferred is encoded in units of a given time t.sub.1 length and the encoded data is sequentially cellulated and sent. The cellulated data is cyclically allocated sequence numbers. When the voice waveform is detected as being silent, it is not encoded, but the sequence number is incremented. FIG. 10 shows one example of cellulated data to be sent. The data includes a cell header part 10 and a cell information part 20. The cell header part includes a portion which in turn includes a sequence number SN and the remaining portion which includes another header element b while the cell information part 20 includes encoded voice information I.
The sent cell is delayed by a predetermined time d.sub.1 in a network and then received. It is then subjected to fluctuation absorption delay by d.sub.2 to absorb a fluctuating delay, reproduced and then decoded. Reproduction of the cell which has been buffered received is performed at the same time interval t.sub.1 as the cell transmission. A sequence number SN allocated to each cell is compared with a reproduction timing number TN. If a cell is not present at that timing, either predetermined interpolation is made or it is processed as being sound-absent or silent.
Recently, a cell transfer system using a variable rate codec is proposed in which information is encoded at a variable rate by the variable rate codec, cellulated to packets of a predetermined length and transferred in an asynchronous manner. However, since each cell is transferred in the asynchronous manner in the cell transfer system using the variable rate codec, there has been a problem that the above-mentioned conventional cell transfer method cannot be applicable for the cell transfer system using the variable rate codec.